The long term goals of the research proposed here is to account for three aspects of speech recognition by patients who use a multichannel cochlear prosthesis: (1) Different initial (1 month) levels of performance; (2) different rates of improvement during the first year of implant use and (3) different terminal levels of performance. Preliminary studies suggest that two factors may account in large measure for the differences in terminal performance: the range of pitch sensation available through the prosthesis and the dynamic range of intensity available to the patient. We propose to assess the relationship between measures of auditory function (pitch scaling, frequency DLs, dynamic range and intensity DLs) and speech recognition (vowel and consonant recognition, spondee recognition, monosyllabic word recognition and recognition of words in sentences) in patients who use the Symbion 4-channel prosthesis. Two experiments are proposed. In one experiment, measures of auditory function and measures of speech recognition will be assessed for patients who have reached an asymptotic level of speech recognition. Four groups of 10 patients will be tested-- two groups with poor speech recognition scores, one group with average speech recognition scores and one group with good speech recognition scores. In the second experiment, the measures of performance will be taken at intervals of 1 month, 6 months and 1 year after patients (n =12) have been fit with a prosthesis. If we can relate differences in speech recognition to differences in auditory function, then we will have gained a major step in understanding speech recognition by patients who use cochlear prostheses.